Host: The Japan Society of Mechanical Engineers
Name : [in Japanese]
Date : September 05, 2021 - September 08, 2021
Cryopreservation is one of the fundamental techniques to maintain the cells for bio-resources as it enables the semipermanent storage of cells. All conventional cryopreservation methods use at least one cryoprotectant agent (CPA) to suppress the generation and growth of ice crystals that damage or destroy the cell structures and/or membranes. On the other hand, any CPAs should ideally be avoided due to their cytotoxicity and potential side effects. Therefore we previously reported a novel cryopreservation method without a CPA based on ultrarapid cooling. In this method, cells were ejected as tiny droplets by inkjet cell printing. The droplets were deposited on the liquid nitrogen cooled substrate and were vitrified (i. e. water molecules were extremely stopped thermal activity as a liquid state), that enables cell cryopreservation. To achieve cell cryopreservation, theoretically, more than approximately 104 °C/s cooling and its 10 times fast warming was required. In this study, we cryopreserved the cells with various cooling rates and warming rates by different substrate materials and thicknesses. Remarkably, the cryopreserved cell viabilities were dependent on substrate thermal conductivity and thermal capacities. As a result, more than approximately 104 °C/ s cooling and warming achieved over 70 % cell viability. However, less than 104 °C/ s warming rate dramatically decreases the viability in spite of ultrafast cooling (approximately 106 °C/ s). We experimentally found that the cell viabilities were influenced by the balance between cooling rate and warming rate in cryoprotectant-free cryopreservation.
